反应详情

Solid carbonyldiimidazole (79.10 g, 0.488 mol) was added to a room temperature solution of N-benzyloxycarbonyl-glycine (117.11 g, 0.560 mol) in anhydrous tetrahydrofuran (THF, 600 mL). The resulting solution was stirred for 45 minutes until C02 evolution had ceased. A solution of L-phenylalanine methyl ester (79.65 g, 0.444 mol) in anhydrous THF (~200 mL) was then added. The reaction temperature was maintained below 40° C. by application of a water bath to the exterior of the reaction vessel. After two hours, a small portion of water (1.5 mL, ~0.08 mol) was added to the reaction mixture to hydrolyze any remaining acylimidazolides and the resulting solution was left to stir overnight. The reaction mixture was concentrated in vacuo and the residual oil was dissolved in ethyl acetate (~1 L). This ethyl acetate solution was extracted with 1 N HCI (2×300 mL--the first aqueous extract was acidified to a pH of 1 by addition of 6 N HCl), water (300 mL), saturated aqueous sodium carbonate (300 mL), half-saturated aqueous sodium carbonate (250 mL), and brine (250 mL). The organic phase was dried by filtration through magnesium sulfate and sodium sulfate and concentrated in vacuo to constant weight. Field desorption mass spectrometry (FDMS) of the resulting oil (160.88 g, ~0.434 mol, 98%) indicated the presence of a single component (M+=370). This material was not further purified, but was instead converted directly into cyclo-glycyl-L-phenylalanine (8) by catalytic hydrogenation (vide infra).

1. temperatureThe reaction temperature was maintained below 40° C. by application of a water bath to the exterior of the reaction vessel
2. waitAfter two hours
3. waitthe resulting solution was left
4. stirringto stir overnight
5. concentrationThe reaction mixture was concentrated in vacuo
6. dissolutionthe residual oil was dissolved in ethyl acetate (~1 L)
7. extractionThis ethyl acetate solution was extracted with 1 N HCI (2×300 mL
8. extractionthe first aqueous extract
9. additionwas acidified to a pH of 1 by addition of 6 N HCl), water (300 mL), saturated aqueous sodium carbonate (300 mL), half-saturated aqueous sodium carbonate (250 mL), and brine (250 mL)
10. dry with materialThe organic phase was dried by filtration through magnesium sulfate and sodium sulfate
11. concentrationconcentrated in vacuo to constant weight